This story is from the category The Brain
Date posted: 24/04/2007
Researchers at Harvard Medical School in the US have discovered the sites to stimulate in the brain of monkeys to feed visual information in, opening the way for artificial, bionic eyes.
The results are a significant step forwards towards use of prosthetic eyes and virtual light systems.
The team used normal-sighted monkeys to test whether stimulating an area of the thalamus deep in the brain could produce a visual signal.
First they trained the monkeys to look at suddenly illuminated points of light.
Then they placed one or two very fine electrodes into the appropriate area of the brain to see what their reaction would be.
They found that the monkeys moved their gaze in the same way they would if a point of light appeared.
However, one or two electrodes is of course, far from being useful for recreating an image. Thousands would be required for even the simplest images. In fact, 128,000 are needed for believed natural resolution of just central sight.
The lead researcher, Dr John Pezaris, research fellow, feels the number of electrodes would have to increase at least 100-fold before this would be useful in patients. Two to three hundred electrodes, before it is of any real use at all. The immediate and obvious problem, is how to get several hundred, or hundred thousand electrodes deep enough into the brain.
To date, the most advanced implanted electrode array has just 12,000 electrodes, and it is a centimetre across.
Ian Andolina, researcher in the UCL Institute of Ophthalmology in the UK, said the experiment demonstrated the principle worked.
"The way this bit of the brain is structured allows you to stimulate the central part of the vision very well, which would be important for conditions such as macular degeneration," he said.
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